Copyright Authorization
A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent disclosure, as it appears in the U.S. Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever.
1. Field of Invention
The field of the present invention relates in general to tunable external cavity lasers, and particularly to an improved tuning system which suppresses mode-hopping and reduces unwanted feedback.
2. Description of the Related Art
Wavelength division multiplexed optical communications systems require compact optical sources which can be tuned to specific channel wavelengths. Prior art is the distributed feedback laser (DFB). Producing a DFB laser for a specific wavelength is a low-yield, statistical process. DFB's are tunable over a few nanometers, but a single DFB cannot be tuned to all of the wavelengths in the communications band (roughly 50-100 nm wide). External cavity semiconductor lasers, on the other hand, can be widely tuned to cover the entire band with a single unit. The common grating-based designs, however, are too large and delicate to be used as installed sources in WDM systems. What is needed is a new type of external cavity laser that has wide-range continuous tuning and possesses a compact, robust, inexpensive form factor.